Heat olive oil in a large pan or wok over medium-high heat. Add the ground beef and cook until browned, breaking it up with a spoon. Remove from the pan and set aside.
In the same pan, sauté onion and garlic for 1–2 minutes until fragrant.
Add bell pepper, carrot, and broccoli. Stir-fry for 3–4 minutes until slightly tender but still crisp.
Return the cooked beef to the pan and stir in the sauce ingredients. Mix well to coat everything evenly.
Pour in the cornstarch mixture and stir for 2 minutes until the sauce thickens slightly.
Remove from heat and garnish with chopped green onions and sesame seeds.
Serving and Storage Tips:
